NVO3 WG T. Ao
Internet-Draft ZTE Corporation
Intended status: Standards Track G. Mirsky
Expires: April 21, 2019 ZTE Corp.
Y. Fan
China Telecom
October 18, 2018
Architecture for Overlay Virtual Sub-Network Interconnection
draft-ao-nvo3-overlay-subnet-architecture-00
Abstract
An virtualized overlay network may be divided into several subnets
for the reasons of geographical location, management, or using
different technologies being used. For example, different customer
have their own preference. But all these subnets need to work
together to provide an end-to-end connectionif in a virtual network,
An extended architecture of the NVO3 and propose a new component to
provide the connection fucntion are introduced in this document.
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Table of Contents
1. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
3. Architecture for subnet . . . . . . . . . . . . . . . . . . . 4
3.1. Stitching NVE . . . . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Normative References . . . . . . . . . . . . . . . . . . 7
5.2. Informational References . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Background
Network virtualization using Overlays over Layer 3 (NVO3) is a
technology that is used to address issues that arise in building
large, multi-tenant data centers that make extensive use of server
virtualization.
As described [I-D.defoy-coms-subnet-interconnection] and
[I-D.homma-coms-slice-gateway], for network slicing in 5G, there are
number of reasons to compose an end-to-end network slice instance by
using subnets and stitching operations, thus enabling hierarchical/
recursive management of slices. These subnets are the part of the
network slice instance, but not isolate from network slice. An
overlay virtual network may also be constructed of several subnets.
In such scenario, subnets interconnection to a virtual network is
required. We also can consider such interconnection as stitiching.
With such stitiching, several subnets can provide a end to end
connection in an overlay virtual network.
Moreover, with the progress in NVO3 WG, some of the data plane
encapsulations have been put forward, some are outstanding dataplane
for an overlay network, such as VxLAN-GPE [I-D.ietf-nvo3-vxlan-gpe],
GENEVE [I-D.ietf-nvo3-geneve] and GUE [I-D.ietf-nvo3-encap], etc.
The consideration about these overlay encapsulations has been
analyzed in [I-D.ietf-nvo3-encap]. The fact is that each of them has
its custmers, and furthermore, some of them have been already
deployed in the network. So that a problem arises: for a virtual
network, all the hosts that connect to the same VN and want to
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communicate with each other are required to have the same data plane
encapsulation. This problem limits the network scalability and
capacity. Especially, when the NVE is located on the vSwitch, the
encapsulation method on the NVE is not predictable. Allowing as many
types of accession as possible is more attractive for a virtualized
overlay network. So in such a scenario, the NVEs using same
techonology can be connected to the same subnet.
To improve the scalability and capacity of the virtualized overlay
network and to satisfy the subnet interconnection requirement in
network slicing, we propose a subnet interconnection architecture in
NVO3, and provide a stitching gateway between the subnets in a
virtual network in this document. With such architecture, the
subnets in an overlay virtual network with different technologies and
with seperate management can be interconnected. The gateway that
provides the connection between subnets is referred to as Stitching
Gateway. In particular, the Stitching Gateway generally would be
located in a certain kind of NVE, such NVE is called as S-NVE in the
following descrption.
2. Conventions used in this document
2.1. Terminology
NVO3: Network Virtualization using Overlay over Layer 3
NVA: Network Virtualization Authority
TS: Tenant System
VxLAN-GPE: Virtual extension LAN with Generic Protocol Extension
GENEVE: Generic Network Virtualization Encapsulation
GUE: Generic UDP Encapsulation
S-GW: Stitching Gateway. A gateway that does the stitching for
seperate subnet to enable them to communicate with each other.
S-NVE: A NVE that complete the stitching functionn as a Stitching
Gateway for subnets in an overlay virtual network.
Subnet: An Overlay Virtual Network is combined with several Subnets
which may use different technology or different management.
Network slice in this document is used as shortened version of
network slice instance.
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2.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Architecture for subnet
As Generic Reference Model desribed in [RFC7364], it's a DC reference
model for network virtualization overlays where NVEs provide a
logical interconnect between Tenant Systems that belong to a specific
VN. But if we need to support a overlay virtual network, an extended
reference model is shown as follows in the NVO3 architecture.
+--------+ +-------+
| Tenant +--+ + TS |
| System4| | /+-------+
+--------+ | .................. /
| +---+ +---------------+
+--|NVE|---+ +---| Stitching NVE |
+---+ | | | (S-NVE) |
/. | | +---------------+
/ . +-----+ .
/ . +--| NVA |--+ .
/ . | +-----+ \ .
| . | \ .
| . | Overlay +--+--++--------+
+--------+ | . | Network | NVE || Tenant |
| Tenant +--+ . | | || System5|
| System3| . \ +---+ +--+--++--------+
+--------+ .....|NVE|.........
+---+
|
|
=====================
| |
+--------+ +--------+
| Tenant | | Tenant |
| System1| | System2|
+--------+ +--------+
Figure 1 Reference Model supporting subnet
Figure 1: Reference Model supporting subnet
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In the above figure, a specific Stitching Gateway(S-Gateway)
component is introduced. Generally, the gateway is located on a NVE,
so we call it as S-NVE. For the TSs in the same virtual network, if
the NVEs which they are connected to are using defferent overlay
technology, want to communicate with each other, Stitching NVE(S-NVE)
should take over responsibilityas a gateway to provide a "bridge" for
the communication. Or for the TSs connecting to different subnets,
but belonging to a virtual network, need to communicate with each
other through S-NVE.
The difference between NVE and S-NVE is that NVE is the connection
between different VN, while S-NVE is the connection between subnet.
From the view of NVE, S-NVE is a intermidiate relay node. For the
two Tenant Systems belong to different subnet have to communicate
through a S-NVE, even though they belong to a same virtual network.
That is, when different NVEs want to set up tunnel, if they can't
connect each other directly because they are on the different
subnets, they can set up a tunnel with S-NVE seperately, so that the
S-NVE connects the two tunnels as a stitcher. There could be more
than one S-NVE in a virtual network.
3.1. Stitching NVE
Stitching NVE(S-NVE) is a certain kind of NVE that maybe appointed by
NVA or by the manager. As an essential component in the NVO
supporting subnet, the requirements for a Stitching NVE is :
1. Provide the connection for the two subnet of a virtual network.
2. Provides identification/ classification of customer and service
traffic, performs the mapping of the two tunnels.
3. Support at least two kinds of encapsulations, translation between
technologies/encapsulations when it is stitching two subnets with two
different technology .
4. Fault and performance monitoring for underlay and overlay
networks.
Regarding the [RFC8014], the Stitching NVE has a reference model as
showed in Figure 2.
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| |
| Data-Center Network (IP) |
+-----------------------------------------------------------+
| | | |
| Tunnel Overlay | | Tunnel Overlay |
+---------+----+ +--+----------+----+ +-----+--------+
| +----------+ | | +--------------+ | | +----------+ |
| | Overlay | | | | Overlay | | | | Overlay | |
| | Module | | | | Module | | | | Module | |
| +----+-----+ | | +---+----------+ | | +----------+ |
| | | | | | | | | |
| NVE1 | | | tNVE| | | | NVE3 | |
| +---+----+ | | +---+-+ +--+--+ | | +--------+ |
| | VNI1 | | | |VNI1 | |VNI1 | | | | VNI1 | |
| +-+------+ | | +-+---+ +-----+ | | +-+------+ |
| | VAP1 | | |VAP1 |VAP2| | | VAP1 |
+----+---------+ | +---------+ | +----+---------+
| +------------------+ |
|\ |
-----+-\------------------------------------------------------+-------
TSI1 |TSI2\ Tenant TSI1 |
+---+ +---+ +---+
|TS1| |TS2| |TS3|
+---+ +---+ +---+
Figure 2 S-NVE Reference Model
Figure 2: S-NVE reference model
S-NVE is a key component of the connection between NVE1 and NVE2. It
can be a dedicated device and be a NVE that also provide the overlay
network for the TSs. When the NVE takes the role of stitching
different subnets for different TSs, it will not forward the traffic
to TS, but to another VAP that supports the encapsulation the
destination NVE owned.
Take the Figure 2 as an example to illustrate how does S-NVE work.
NVE1 belongs to subnet1 and only support VxLAN-GPE, and NVE2 belongs
to subnet2 and only support GENEVE. For the two communicating TSs:
TS1 needs to send packets to TS3, and TS3 also needs to reply to TS1.
They are in the same VNID1, but the NVE they are connected to is
using a different encapsulation, and the they belongs to two
different subnet. So if the two TSes want to communicate with each
other, packets have to transfer at S-NVE first. For NVE1, it has no
sense that TS3 is connecting to NVE3, instead of assuming that TS3 is
connecting to S-NVE. In the same way, for NVE3, it has no sense that
TS1 is connecting to NVE1, instead of assuming that TS1 is connecting
to S-NVE. So because of the existence of the tNVE, no matter TS1/TS3
or NVE1/NVE3, they never perceive that they are in the different data
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plane. NVE1 getting the packets from TS1 encapsulates them in Vxlan-
GPE and then send the packets to S-NVE. The S-NVE receives the
packets from the Vxlan-GPE tunnel and then de-encapsulate the vxLAN-
GPE to VAP1. Next, the S-NVE forwards packets to the Overlay Module
from VAP2 to have another encapsulation GENEVE on the packets. At
last S-NVE forwards the packet in the GENEVE tunnel to NVE3.
From the above, S-NVE is like a stitcher between TS1 and TS2. And
owning to S-NVE, even though NVE1 and NVE2 which TS1 and TS2
connecting belong to separate subnets and seperately have different
encapsulation, as long as they are in the same virtual network, they
would communicate each other as a Larger L2 network and no need to
know that they are in different subnets or using different
technology.
4. IANA Considerations
TBD.
5. References
5.1. Normative References
[I-D.ietf-intarea-gue]
Herbert, T., Yong, L., and O. Zia, "Generic UDP
Encapsulation", draft-ietf-intarea-gue-06 (work in
progress), August 2018.
[I-D.ietf-nvo3-geneve]
Gross, J., Ganga, I., and T. Sridhar, "Geneve: Generic
Network Virtualization Encapsulation", draft-ietf-
nvo3-geneve-08 (work in progress), October 2018.
[I-D.ietf-nvo3-vxlan-gpe]
Maino, F., Kreeger, L., and U. Elzur, "Generic Protocol
Extension for VXLAN", draft-ietf-nvo3-vxlan-gpe-06 (work
in progress), April 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
.
[RFC7365] Lasserre, M., Balus, F., Morin, T., Bitar, N., and Y.
Rekhter, "Framework for Data Center (DC) Network
Virtualization", RFC 7365, DOI 10.17487/RFC7365, October
2014, .
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[RFC8014] Black, D., Hudson, J., Kreeger, L., Lasserre, M., and T.
Narten, "An Architecture for Data-Center Network
Virtualization over Layer 3 (NVO3)", RFC 8014,
DOI 10.17487/RFC8014, December 2016,
.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, .
5.2. Informational References
[I-D.ao-nvo3-multi-encap-interconnect]
Ao, T., Mirsky, G., and F. Yongbing, "Multi-encapsulation
interconnection for Overlay Virtual Network", draft-ao-
nvo3-multi-encap-interconnect-00 (work in progress), March
2018.
[I-D.defoy-coms-subnet-interconnection]
Foy, X., Rahman, A., Galis, A.,
kiran.makhijani@huawei.com, k., Qiang, L., Homma, S., and
P. Martinez-Julia, "Interconnecting (or Stitching) Network
Slice Subnets", draft-defoy-coms-subnet-interconnection-03
(work in progress), March 2018.
[I-D.homma-coms-slice-gateway]
Homma, S., Foy, X., and A. Galis, "Gateway Function for
Network Slicing", draft-homma-coms-slice-gateway-01 (work
in progress), March 2018.
[I-D.ietf-nvo3-encap]
Boutros, S., "NVO3 Encapsulation Considerations", draft-
ietf-nvo3-encap-02 (work in progress), September 2018.
[RFC7364] Narten, T., Ed., Gray, E., Ed., Black, D., Fang, L.,
Kreeger, L., and M. Napierala, "Problem Statement:
Overlays for Network Virtualization", RFC 7364,
DOI 10.17487/RFC7364, October 2014,
.
Authors' Addresses
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Ting Ao
ZTE Corporation
No.889, BiBo Road
Shanghai 201203
China
Phone: +86 21 68897642
Email: ao.ting@zte.com.cn
Greg Mirsky
ZTE Corp.
1900 McCarthy Blvd. #205
Milpitas, CA 95035
USA
Email: gregimirsky@gmail.com
Yongbin
China Telecom
No.109, Zhongshan Avenue
Guangzhou 510630
China
Email: fanyb@gsta.com
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